What's new
What's new

Question About CNC, what machine do I Need .

spurst

Member
Hello I am new here, so please be gentle. I am making Worms And Shafts for a tool we sell out of 304 stainless, make about 500 each, every three months they are casted then turned by china no good 20+ 0/0 scrap rate. One worm is 60 degree thread, 0.147 deep, 4 TPI, one inch long, 1.05 Dia with a thru hole 1/2" that has to be close to tolerance for press fit to shaft, and the other one is same only smaller with 5 TPI, and the shafts are straight forward just three steps in size from 5/8" down to 1/4" 2.40" long also Stainless. My Question is, we want to get rid of casting, or casted then we do the machining, or just make them from rod stock. I have no CNC experience, just manual lathe and slow. If we were to get a used CNC lathe, what would we need to turn these parts, room is limited space in climate controlled part of our shop. The 2 shafts and 2 worms is all it would be used for. Thanks for any HELP
 

DDoug

Active member
Hello I am new here, so please be gentle. I am making Worms And Shafts for a tool we sell out of 304 stainless, make about 500 each, every three months they are casted then turned by china no good 20+ 0/0 scrap rate. One worm is 60 degree thread, 0.147 deep, 4 TPI, one inch long, 1.05 Dia with a thru hole 1/2" that has to be close to tolerance for press fit to shaft, and the other one is same only smaller with 5 TPI, and the shafts are straight forward just three steps in size from 5/8" down to 1/4" 2.40" long also Stainless. My Question is, we want to get rid of casting, or casted then we do the machining, or just make them from rod stock. I have no CNC experience, just manual lathe and slow. If we were to get a used CNC lathe, what would we need to turn these parts, room is limited space in climate controlled part of our shop. The 2 shafts and 2 worms is all it would be used for. Thanks for any HELP

Why not simply get a machine shop stateside to make them for you ?
Why are they "Casted" first ?
Machining from solid might prove cheaper.

There are some shops specializing in extrusion screws, that sound like what you have there.
 

EmanuelGoldstein

Active member
Short for "worm gear".
No, the worm is the part with the thread. Wormgear is the roundy one with teeth around the edge. At 20 a month, it's silly to think nc. Simple part to make manually. But I can see how they are having trouble because this description is out there ... several people here could do these but I dunno, this type of customer can be a bit of a problem.
 

mhajicek

Active member
No, the worm is the part with the thread. Wormgear is the roundy one with teeth around the edge. At 20 a month, it's silly to think nc. Simple part to make manually. But I can see how they are having trouble because this description is out there ... several people here could do these but I dunno, this type of customer can be a bit of a problem.

Ok, technically correct, the worm gear runs against the worm. I learned as a kid that the "worm" was a "worm gear" and it stuck.

LEGO Worm Gear with Old Axle (4716) | Brick Owl - LEGO Marketplace
 

spurst

Member
I did get a machine shop stateside to quote them and are ten times the price. I am not sure if they cast the worms but the shaft has to be casted because of other features that would be to costly to machine and there is only one surface on the shaft that has to be close tolerances. The trouble we have is there machine shop cant hold a tolerance for a press fit (worm to shaft.)
 

DDoug

Active member
I did get a machine shop stateside to quote them and are ten times the price. I am not sure if they cast the worms but the shaft has to be casted because of other features that would be to costly to machine and there is only one surface on the shaft that has to be close tolerances. The trouble we have is there machine shop cant hold a tolerance for a press fit (worm to shaft.)

Post up a print so we can help more.
 

mhajicek

Active member
I did get a machine shop stateside to quote them and are ten times the price. I am not sure if they cast the worms but the shaft has to be casted because of other features that would be to costly to machine and there is only one surface on the shaft that has to be close tolerances. The trouble we have is there machine shop cant hold a tolerance for a press fit (worm to shaft.)

Before you described a worm with a simple stepped shaft. I don't think anyone can recommend a machine or process without seeing the part or print if it's more complicated than that. But to punt, for 20pc per month, 5 axis milling would be cheaper than casting + machining in the vast majority of cases.

No, it won't be as cheap as China, but your parts from China seem to have been worth what you paid for them.

Oh, and don't get "a" machine shop to quote them, get at least three. Prices and quality will vary wildly from shop to shop, not necessarily in sync.
 

BobM3

Member
You're cutting the teeth (threads) and/or just the blanks? Usually worm threads are done with a worm milling machine (if soft material) or a grinder (if hard). They can sometimes be done on a CNC lathe.
 

spurst

Member
You're cutting the teeth (threads) and/or just the blanks? Usually worm threads are done with a worm milling machine (if soft material) or a grinder (if hard). They can sometimes be done on a CNC lathe.

Yes we would like to cut the teeth on the worm not just the blanks they do it with a lathe because you can see chatter marks on the worm it self they are not hard the parts turn with a hand drill slow and short duration. I would upload a picture if i could figure out how to attach a file to this forum. I have cut a lot of them on a Manuel lathe (kinda a lathe) a little south bend but dang its slow. Feller would starve to death cutting them on it.
 

DDoug

Active member
Yes we would like to cut the teeth on the worm not just the blanks they do it with a lathe because you can see chatter marks on the worm it self they are not hard the parts turn with a hand drill slow and short duration. I would upload a picture if i could figure out how to attach a file to this forum. I have cut a lot of them on a Manuel lathe (kinda a lathe) a little south bend but dang its slow. Feller would starve to death cutting them on it.

I caught a fish one time In lake Erie....It was this big.....:skep:

Your waving your arms around, but we need a drawing, with tolerances.
 

spurst

Member
I dont have the drawings here at home. The only really critical tolerance is between the worm and the and the shaft on the larger shaft interference of 0.004 +0.002 -0.00 And the smaller shaft in the picture no worm here for it, the interference needs to be .0025 + 0.001 -0.000 I will try to upload a picture assembled so you can see were it presses on
 

Garwood

Active member
Why can't these parts be made from solid cost effectively?

Why not post a RFQ on this site before trying to figure this out for yourself?


I make products. When I started out I had no clue. I just knew what I wanted to make. I didn't ask a bunch of questions on the internet. I talked to every local shop. I bought many lunches and beers and I hired a programmer to get me up and going right away, teach me how to use the machines I bought and answer my stupid questions.
 

mhajicek

Active member
Based on what I can see, those should be simple 2 axis lathe parts, with rotary broaching for the hex socket, and some knurling on the one. No reason to cast anything.
 

spurst

Member
thanks does a smaller cnc lathe have enough power to rotary broach a 5/16 hex hole because I dont have enough lead in my pants to do it with that little lathe or a bridge port knee mill I have the tools and tried I can on the mill if you over size the pilot hole a little and have a cheater on the quill handle, I would like not to have the shaft or worm casted if possible, when they do it wrong always too big a hole in the worm, i cant repair it then we have to wait 4 months for the next order to get here. The first 5000 units were great only maybe 10 bad ones then they must have had a high fever now the last two orders of a thousand 243 were good. There castings are really good but there machining sucks the shaft are never concentric with the hex hole either and on the other 2 flats on the shaft in runs in a bronze bushing.
 








 
Top